The invention concerns a method of starting an electronically commutated direct-current motor with several cyclically activated coils by means of commutating signals emitted while the motor rotates.
There is always a problem involved in detecting and processing the actual direction and phase relation of rotation of motors of this type. Using several sensors to detect the direction and phase relation for example is known. The sensors, however, make the device more expensive. Systems with only one sensor that process the differently coded sensed scanned signals in order to detect direction and phase relation are also known. This solution, however, cannot be employed to correctly process the different codes below a prescribed minimum motor speed, at which point there is a substantial period during motor start-up when phase relation and direction of rotation do not conform to what has been set.
Getting a motor of the aforesaid type into the correct direction of rotation by initially stationing it in a prescribed position is also known. During this positioning period the commutation indexing is disengaged, and the commutation stage will only start the motor up from this prescribed initial state once the positioning phase is over.
It is important for a motor, especially one that drives the head drum in a videorecorder, to start moving in the correct direction as soon as possible, before the magnetic tape is threaded in.